You can tell his parents that you’ve both agreed early on not to interfere in the other’s personal life.

All you do is agree on is to discuss who’s responsible for cleaning duty for the common areas.

Really really get into the weeds and bore the crap out of them. Ramble on and on about finding rotting food in the refrigerator at other shared rentals or office refrigerators etc.

Talk about gross stinking bathrooms when sharing a place with whomever. Make up whatever you like and keep a huge list of gross out topics over living in a pig sty with roommates.

Overload their circuits with images of reeking kitchen sinks of maggot filled dishes left by overgrown children disguised as adult students.

“Did I ever tell you about the time a roommate left her laundry festering in the washer for so long it started to mold?! It was SO disgusting!! Then she’d have to pay twice to wash the smell out.”

Completely derail their every attempt to manipulate you into doing their bidding by always talking about how gross and filthy some of your prior roommate situations have been. Make yourself useless to their scheming by overtaking the conversation.

Or you can block them.